Objective and goals: To find a clue for the mechanism of drug resistance in TRA-1-60 positive minor cell populations Overall design: We examined TRA-1-60 positive and negative population in FL-18 and DOHH-2 cell line using Agilent 8 x 60K microarray to identify the specific genes that are involved in the drug resistance mechanisms. TRA-1-60 positive and negative population were purified using FACS Aria. Total RNA was extracted and analyzed.